1. Field of the Invention
This invention relates generally to an apparatus for freezing an encapsulated ice substitute and a process for freezing such ice substitutes using the invented apparatus, and in particular, to a process for freezing a capsule belt having a plurality of rows of capsules, each of which contains a thermal controlling agent.
2. Description of the Related Art
The use of ice or dry ice as a coolant material serves to preserve organic material and inhibits the growth of many harmful micro organisms.
The major drawback to using ice as a coolant material is that it melts. If the ice is used as a packing material, the space taken up by the ice when melted will be less than when it is frozen, so that it will no longer be an effective packing material. The melted ice is easily contaminated by microorganisms and, since it will be in intimate contact with the products it is intended to protect, these are also liable to become contaminated. The products may also be damaged by getting wet. The melted ice will also allow the products to move or slosh around in the container, risking damage by impact with the walls of the container.
Dry ice has similar problems in that it sublimes into gaseous CO.sub.2 with time. The gas must be dissipated and, with the solid CO.sub.2 gone, the product will no longer be packed against movement in its container. Also both ice and dry ice can be used only once, adding to the expense of such thermal storage.
U.S. Pat. No. 4,931,333 discloses a method for making an ice substitute which is an improvement over known coolants such as ice and dry ice. According to that invention, the ice substitute comprises a plurality of capsules each having a flexible outer skin containing a thermal controlling agent which can maintain a predetermined temperature range for an extended period of time. The thermal controlling agent contained in the capsules is a eutectic solution which has the capacity to absorb or release heat with little or no change in temperature while in the process of changing from one physical state to another, e.g. solid to liquid or vice versa. The capsules must first be charged with the eutectic solution and frozen to the phase change temperature or lower before being subjected to the intended use. However, charging or freezing such ice substitute to the phase change temperature is costly and time consuming because the process can take up to 20 hours using the conventional blast freezing method. Moreover, the equipment for blast freezing the ice substitute is large and inconvenient to operate.
Methods for quick freezing vital body fluids such as sperm, eggs, zygotes, blood and the like, for freezing human tissue and organs, and for freezing other biological materials are known.
U.S. Pat. No. 4,401,909 discloses a method of freezing fishery products. The method includes the steps of preparing a brine containing rapeseed oil, propylene glycol, calcium chloride and water, cooling the brine and immersing the seafood in the cooled brine until it is frozen. A process for quick freezing of meat such as beef, poultry, pork, fish and the like in a similar brine is disclosed and claimed in U.S. Pat. No. 4,654,217 issued to the same inventor.
U.S. Pat. No. 4,657,768 discloses a freezing method for perishable foods which includes placing a perishable food in a heat conducting container. The opposite surface of the heat conducting container is then placed into contact with a cooled brine or a liquified gas. Accordingly, the perishable food is frozen quickly without immersion of food in the cooled brine or liquified gas.
U.S. Pat. No. 4,689,963 relates to a method of freezing foods, in which a layer of a rapeseed oil containing brine is placed in the heat conducting container along with the perishable food.
U.S. Pat. No. 4,840,034 discloses a method of freezing body fluids for extended storage. The method includes the steps of preparing a brine including a suitable oil, generally a cruciferous oil; cooling the brine to a temperature between about -22.degree. and about -43.6.degree. F. The brine generally includes a glycol, a salt and water in addition to the suitable oil.
U.S. Pat. No. 4,840,035 discloses a method of freezing tissue for cytological or histological examination. The method uses a brine similar to that disclosed in U.S. Pat. No. 4,840,034.
U.S. Pat. No. 5,001,047 also discloses a method to chill human organs and maintain the viability of the organs, employing a brine similar to that used in U.S. Pat. No. 4,840,034.
There is no teaching or suggestion in any of these patents that these processes can be used to make ice substitutes such as capsule belts or sheets in a convenient and economical fashion. The inventor has made this discovery which presently speeds up the process and markedly reduces the cost. Accordingly, it is desirable to provide a process for quick freezing ice substitutes.